Magnetic lock



Sept. 20, 1955 P. s. GRlERsoN MAGNETIC LOCK Filed May 2l, 1954 INVEI'TOR Rm] 5.6111625022 Unite States Patent Gillice 2,7l8,424 Patented Sept. 20, 1955 MAGNETIC LGCK Paul S. Grierson, Maplewood, N. J., assignor to Thomas A. Edison, Incorporated, West Grange, N. J., a corporation of New Jersey Application May 21, 1954, Serial No. 431,348

7 Claims. (Cl. 292-285) This invention relates to magnetic locks and particularly to magnetic locks adapted for use on cases for mine lamp batteries.

It has long been a requirement of the United States Bureau of Mines that cases for mine lamp batteries be locked closed to prevent the miner from opening the case, either by intention or accident, and possibly tampering with the battery or producing a spark such as might possibly set off an explosion in the mine. Magnetic locks have been used with considerable success for this purpose, since they require a special magnet, generally not available to the miner, to open the lock and since the locks may be built to conceal the required mode of application of the magnet. However, the locks which have been heretofore made have not been entirely foolproof in that they have been susceptible of being opened by a sharp properly directed knock. As people have become familiar with the locks from long use, some have learned the trick of knocking them open. Accordingly, there has arisen a need for a still more dependable type of magnetic lock than has been heretofore available.

The present invention resides in a novel form of magnetic lock which is not susceptible of being knocked open. The present improvement resides in a rotary latching structure which is dynamically balanced and biased with sucient force to prevent its displacement from a latching position by any mechanical knock or by any sharp rotary movement of the lock or battery case. An ancillary feature of the invention resides in biasing the cover open and in utilizing this biasing force to exert an additional mechanical inuence effective to hold the rotary latching structure in latched position.

The biasing force on the cover provides also a safety feature to prevent unauthorized opening of the lock since this biasing force must be relieved from the lock by pressing the cover inwardly before the lock will respond to an external magnetic field. Also, as will appear, the magnetic field must be maintained on the lock not only during the initial inward pressing of the cover but also until the cover is moved open beyond its latched position in order to unlock the cover. in view of these requirements and the fact that the magnetic field must be applied in a particular direction not discernible to one unfamiliar with the lock, the present magnetic lock is a particularly safe one for use in mine lamp equipment or wherever unauthorized opening of the lock is not desired.

Accordingly, objects of my invention are to provide an especially reliable magnetic lock which is not susceptible of being knocked open or being opened by any external forces or movements of the lock as a whole. Another object is to provide such magnetic lock which requires both a predeterminately directed magnetic field and a concurrent manipulation of mechanical forces to open it, none of which can be discerned from outward appearance of the lock. A still further object is to provide such improved lock which is especially adapted for use in connection with mine lamp equipment, and whichl is simple in construction, sturdy and reliable, and economical to manufacture.

These and other objects and features of my invention will be apparent from the following description and the appended claims.

In the description of my invention reference will be had to the accompanying drawings, of which:

Figure 1 is a fractional side elevational view of a mine lamp battery casing on which my magnetic lock is applied;

Figure 2 is a fractional front elevation of this casing and lock;

Figure 3 is a fractional sectional view taken on the line 3 3 of Figure 2 and showing in dash-dot lines the relative positioning of a permanent magnet for opening the lock;

Figure 4 is a front elevation of the container showing loop and catch elements of the lock structure, which are permanently mounted on the casing, and showing in dashdot lines the position of the latching element of the cover as the latching element is being moved into interlocking engagement with the catch element, and showing in cross section the interlocking position of the latching element with the catch element;

Figure 5 is an enlarged sectional view of the lock structure when in locking position, taken on the line 5-5 of Figure 6;

Figure 6 is an enlarged medial sectional View of the lock structure, taken on the line 6 6 of Figure 2; and

Figure 7 is a fractional rear view of the component of the lock structure hinged to the cover, showing the positioning of the magnetic element of the lock structure in dotted lines.

Batteries for mine lamp services are housed in strong, rugged cases made, for example, of welded steel construction. As shown in Figures l and 2, such a case comprises a deep container itl, fractionally shown, typically of an oblong shape as viewed from the top and ends, and a relatively shallow cover 1l which may overlap the rim of the container when in closed position. One end of the cover is hinged at 12 to a bracket 13 itself riveted to the container. The other end of the cover is to be locked closed in the position shown in Figure l, which is accomplished by a magnetic lock 14 according to my invention. The cover is biased open against the holding forcel of the lock 14, to seek a partially-open position, by means of two internal springs l5 of U shape, which are riveted to the upper wall of the cover and which bear with pressure against respective upright posts 16 of the battery when the cover is closed. As will appear, this upward biasing of the cover is adapted to perform useful functions in retaining the lock 14 in locked position and in safeguarding the lock from unauthorized opening.

The lock i4 comprises a strap 1'7 having a curled upper end portion pivotally embracing the central part of a cross pin 1S mounted on the cover, the mounting for the cross pin comprising a lC-shaped bracket i9 secured as by welding to the end wall of the cover and having curled end portions embracing the ends of the pin. The strap depends downwardly by force of gravity to overlap the front upper portion of the container ld, and is curved inwardly at its lower end to cause it to enter naturally a loop on the end wall of the container as the cover is closed, the loop being formed by a U-bracket 21 secured as by spot welding to the end wall. To facilitate the entry of the strap into the loop, the upper edge of the bracket 21' is provided with an outwardly-curved lip 22. The bracket 21 is quite shallow so that it serves `to retain the strap in close juxtaposition with the end wall of the container when the container is closed (Figure l).

A central portion 17a of the strap has side extensions to provide it with a greater width as shown in Figure 7.vl

Mounted on this central portion of the strap is a small circular housing-23 for the rotary latch structure of the lock. This housing has a rectangular base 25 provided with reenforcing side iianges 26 which curve inwardly at the ends as at 27. The base is mounted ilat against the strap with the side ilanges enveloping the side edges of the strap portion 17a, and is retained thereon by rivets 28 at the corners of the base. The circular housing 23 is formed integrally with the base by a deep drawing operation. In this drawing operation the outer circular wall 29 of the housing is made cone-shaped (Figure 6) to give the housing greater strength and rigidity, and the central portion of the coned wall is further deep-drawn to provide an internal well 30 which serves as a bearing for the rotary latching structure abovementioned.

The rotary latching structure comprises a iatching bar 24 of rectangular shape formed on the end of a shaft 31 by cutting away opposite segments of the shaft. The inner end of this shaft is pivoted in the bearing 3G and the outer end thereof is pivoted in a circular opening 32 in the strap portion 17a. The shaft is retained in position by abutment of a shoulder 33 thereof against the strap, in which position the latching bar at the end of the shaft projects beyond the strap as shown for example in Figure Within the housing 23 there is abar 34 of magnetic material-hereinafter referred to as the magnetic barwhich is mounted at its center on the shaft 31. interposed between this shaft and the housing is a torsion spring 35 having one end anchored to the bar 34 and the other end secured to the strap as by engagement of an end port1on of the spring into a groove 17b in the strap covered by the rim of the base of the housing 23. In response to this torsional biasing, the rectangular latching bar is yieldably held rotationally in a crosswise position shown in the figures, which position is deiined by abutment of the magnetic bar 34 against a stop pin 35a secured to the wall 29. The magnetic bar 34 has arcuate poles 34a extending counterclockwise from its outer end portions, as it appears in Figure 5. These pole portions have an arcuate length of about 90. By the provision of these arcuate pole extensions, it is assured that-when a horseshoe magnet M is positioned crosswise to the magnetic lock with its poles embracing the housing 23 as indicated in Figure 3, the rotary latching structure will be propelled in a counterclockwise direction through approximately 90 to place the latching bar 24 at right angles to the positions shown in the iigures-Which is the unlatching position of the latch bar as will appear.

Cooperating with the latch bar 24 to lock the case is a catch member 36 secured as by welding to the front end wall of the container 10 in a position above the bracket 21. This catch member has a central slot 37 open to the top and of a width suflicient to admit the latch bar only when the latch bar is in alignment therewith, the slot 37 being for example just slightly wider than the width dimension of the latch bar and being substantially narrower than the length dimension of the latch bar. However, the slot 37 opens into a clearance space 38 at its lower end, which space is sufficient to permit turning of the latch bar therewithin. The space 38 is bounded at the top by edges of the catch member extending at right angles to the slot to form two shoulders 39 against which the ends of the latch bar abut when the latch bar is interlocked with the catch member (Figure 4).

The right side wall of the slot 37 is extended upwardly and is curved to form a cam face 40. As the cover is closed the right end of the latch bar is impinged against this cam face and turned counterclockwise into alignment with the slot, and then it is moved into the slot. Upon pressing the cover onwardly beyond the position in which it becomes eventually latched, the trailing edge of the latch bar is moved free of the right wall of the slot and is thereupon snapped clockwise by the torsional spring 35 into its crosswise latching position. Upon subsequently releasing the cover, the cover springs backwardly until the ends of the latching bar abut against the shoulders 39.

To release the lock three operations must be performed in proper order and time relation: (l) the cover must be depressed sufficiently to displace the latch bar 24 from the shoulders 39 and permit free turning of the bar within the space 38, (2) the magnet M must be applied to the lock, while the cover is so depressed, to turn the latch bar into alignment with the slot 37, and (3) the cover must be released While the magnet is so applied to the lock to enable the latch bar to enter and pass through the slot. In view of the necessity of performing this plurality of operations in the manner here described, and the fact that these operations cannot be discerned either individually or collectively from the outward appearance of the lock, as well as the fact that the positioning of the permanent magnet can also not be discerned, the present lock is especially foolproof against unauthorized opening even if the miner has in his possession a magnet for opening the lock.

Additionally, it will be observed that it is impossible to open the lock by any mechanical blow or by any sharp motion of the lock as a whole. For instance, the rotary latch structure comprising the latch bar 24, shaft 3l and magnetic bar 34 has a very small moment of inertia and is dynamically balanced so that it is not suceptible of rotational movement in response to any movement imparted to the lock as a whole or any external knock applied to the lock. Also, the rotary latch structure is biased by the torsion spring 35 with suicient force to prevent it from being displaced accidentally from a latching position. Still further, while the battery case is latched closed the outward biasing of the cover presses the latch bar continuously against the shoulders 39 to insure further against any accidental displacement of the latch bar into an unlatching position enabling it to be moved through the slot 37 free of the catch member 36. All of these features cooperate to prevent any accidental or unauthorized opening of the lock by any means or in any accidental manner without the use of a suitable magnet for turning the rotary latching structure into its unlatcning position.

The embodiment of my invention herein particularly shown and described is intended to be illustrative and not necessarily limitative of my invention since the same is subject to changes and modiications without departure from the scope of my invention, which I endeavor to express according to the following claims.

I claim:

l. A magnetic lock for latching cover and container elements comprising a strap hinged to one of said elements in position to overlie a portion of the other when the cover is closed; a loop on said other of said elements adapted to receive said strap; engageable interlocking members on said strap and other element comprising a pivoted latching bar and a catch member having a narrow slot adapted to receive said bar only when the bar is pivotally oriented into alignment with the slot, said catch member having shoulders at the inner end of said slot for locking engagement with the ends of said latching bar when the latching bar is in a crosswise position beyond the inner end of the slot; means pivotally biasing said bar into said crosswise position; a member of magnetic material secured to said latching bar with its magnetic axis extending crosswise of its pivot axis; and a nonmagnetic housing concealing the positioning of said magnetic member, said magnetic member being responsive to a magnetic field predeterminately directed with respect to said housing for turning said latching bar into alignment with said slot for release of the latching bar from said catch member.

2. The combination set forth in claim l including means for yieldingly urging said bar and catch member apart in a direction along said slot to hold said bar with pressure against said shoulders while said cover is latched closed, said urging means being yieldable to pressure exerted on said strap in a direction inwardly with respect to said loop whereby to free the latching bar of said shoulders and permit the latching bar to be aligned with said slot in response to an externally-applied magnetic field.

3. The combination set form in claim 1 wherein said latching bar is mounted on said strap, and wherein said housing constitutes a cylindrical formation extending outwardly from said strap and adapted to be received between the poles of a magnet to cause said latching bar to be turned into a releasing position without revealing the positioning of said magnetic member.

4. The combination set forth in claim l wherein one side wall of said slot constitutes a cam member adapted to impinge against one end of said latching bar to turn the latter into alignment with said slot as said strap is inserted into said loop.

5. The combination set forth in claim 1 wherein said magnetic bar has peripherally extending pole pieces adapted to enable the magnetic bar to respond to a magnetic field transverse to the pivot axis of the magnetic bar through an angular distance of substantially 90.

6. A magnetic lock for latching a hinged cover of a mine lamp battery case to the case proper, comprising a strap hinged to the free end of said cover and depending downwardly under influence of gravity beyond the lower edge of the cover; loop means on a side wall of said case adapted to receive said strap as the cover is closed; a catch member on said side wall having a vertical slot open at the top and terminating into a space at the bottom with formation of shoulders at the lower ends of the slot; a latching bar pivoted to said strap and biased into a position wherein it is crosswise to said slot, said latching bar having a lesser width dimension than the width of said slot and a greater length dimension than the width of said slot to permit it to traverse said slot only when in alignment therewith, said cover being mounted for limited over-travel beyond closed position to allow said latching bar to be moved free of said slot and to turn crosswise thereto in response to the biasing thereof;

means yieldingly urging said cover from a closed position to retain said latching bar in engagement with said shoulders; a magnetic member secured to said latching bar for turning the latter into alignment with said slot upon subjecting the magnetic bar to a predeterminately directed magnetic field while the cover is pressed inwardly to free the latching bar from said shoulders; and a circular nonmagnetic housing on said strap for concealing the positioning of said magnetic member.

7. A magnetic lock for interlocking two members in overlapping relation to each other; loop means on one of said members for receiving the other member and retaining the members in close juxtaposition with each other; a catch member on the confronting face of one of said members having a slot open at the ends and extending in the direction of disengaging movement of said members; a pivoted latching bar on the other of said members and projecting therefrom for engagement with said catch member, said latching bar being biased crosswise to said slot and being adapted to pass through said slot as said members are moved into overlapping relationship only when the latching member is aligned with the slot; means for moving the latching bar in alignment with said slot as the members are moved into interlocking position, said members being mounted for over-travel from their interlocking position to permit the latching bar to move beyond said slot and turn crosswise thereto in response to the biasing thereof for locking engagement with a portion of the catch member beyond said slot; and magnetic means associated with said latching bar to enable the latching bar to be turned by a magnetic field into alignment with said slot for release of the bar from said catch member through said slot.

References Cited in the file of this patent UNITED STATES PATENTS 1,025,394 Gottschalck May 7, 1912 1,743,540 Gossmann et al. Jan. 14, 1930 2,592,207 Stamper Apr. 8, 1952 

